Japanese yew bonsai

Placement

Japanese yew lives outdoors all year. It appreciates good light but tolerates shade, although in deep shade its branching becomes less dense. A bright spot with some partial shade suits it well: in hot, dry climates, protect it from strong afternoon sun in summer.

Winter. It is one of the hardiest yews. The tree survives nights below -4 °F, but in a pot its roots are exposed: from about 14 °F, insulate the pot or bury it. Where nights often fall below that threshold, a cold frame or unheated greenhouse becomes useful. Wait for the first frosts before moving it to shelter, and never bring it into a heated room: it needs winter cold. The real danger is frost combined with bright sun and icy wind, which damages both the tender roots and the foliage.

Pests. Black vine weevil is the worst: the night-feeding adults chew needles and bark, while the grubs hide in the root ball and eat the roots, often with no visible sign until the tree declines. Yew scale, mealybugs and tortrix moth caterpillars can also move in. Overwatering leads to root rot, the only truly common disease.

Soil mix

Yew hates soggy soil, so use a very free-draining mix. It is especially fond of pumice. A common conifer mix is one third akadama, one third pumice and one third lava rock. In hot climates, add a little humus to hold more water; in very wet climates, add more lava rock instead. Yew tolerates a pH between 5 and 8.

Watering

Water as soon as the mix starts to dry, but don’t keep the roots wet all the time. To know when to water, push a finger about 0 in into the mix: if it comes out dry, water until it runs from the drainage holes. Misting the foliage with lime-free water is beneficial. In winter, water only when the mix dries.

Fertilizer: during the growing season, apply a solid organic fertilizer every four weeks, or a liquid fertilizer every week. No fertilizer in winter.

Pruning

Japanese yew accepts pruning back into old wood and buds readily there; after hard pruning, it can even sprout from areas with no needles left at all.

• Pinching: as shoots grow, pinch or pluck them by hand rather than cutting with scissors, which turns the cut needles brown. To keep fruit on a female tree, stop pinching after spring flowering.
• Thinning: in summer, remove old needles so light reaches the interior of the tree and back-budding is encouraged. In late fall, plucking two- and three-year-old needles almost always triggers new buds in spring at the very spots where they grew.
• Structural pruning: heavy cuts and branch removal are best done in fall.

Deadwood. This is one of the great attractions of old yews. Their very hard wood lends itself to carving jin (stripped branches) and shari (bare trunk sections), and old trunks develop raised live veins. Before stripping bark, locate the essential live veins and trace them up from the base; don’t create a shari directly below a living branch. Start with a narrow strip and spread the work over several months or even years, in early spring or late summer, then protect the wood with lime sulfur. At the Omiya Bonsai Art Museum, a Japanese yew about two centuries old shows a white shari covering most of its trunk; in Washington, a tree collected on the island of Hokkaido and in training since 1966 was carved to look like the natural dieback of an old tree.

Styles: all suit it except broom. Trunks tend to stay fairly slim; on old specimens, a heavy trunk usually results from several trunks fusing together.

Propagation: sow seeds outdoors in fall as soon as they ripen, with germination that can take two years or more and yields mostly male trees; take semi-ripe cuttings from late summer to early fall; layer in late spring.

Wiring

Wiring can be done at any time of year, but only on a vigorous tree: a weak yew must regain strength first, and a freshly repotted tree should not be wired. Young twigs are flexible and bend easily, but old branches become stiff and hard to bend. Firmer copper wire suits conifers well; aluminum wire is easier to handle for beginners. Choose wire about one third as thick as the branch, wound at roughly 45°. For branches that are too thick or stiff, use a guy wire. Conifers keep their wire longer than deciduous trees, but check it often: it can bite in within one to four months.

Repotting

Repot every two to four years; very old trees can wait longer. Do it in spring, as the buds begin to extend; late summer, when roots are most active, also gives good results. The roots tolerate fairly heavy pruning. Use the opportunity to inspect the root ball for vine weevil grubs, then replant in the free-draining mix described above. Wear gloves while handling the tree: every part of the yew except the red flesh of the aril is toxic.